{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-63984", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-19T07:54:57.025Z", "datePublished": "2026-07-19T14:56:06.786Z", "dateUpdated": "2026-08-05T12:37:52.442Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:37:52.442Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()\n\nipv6_rpl_srh_decompress() computes:\n\n outhdr->hdrlen = (((n + 1) * sizeof(struct in6_addr)) >> 3);\n\nhdrlen is __u8. For n >= 127 the result exceeds 255 and silently\ntruncates. With n=127 (cmpri=15, cmpre=15, pad=0, hdrlen=16):\n\n (128 * 16) >> 3 = 256, truncated to 0 as __u8\n\nThe caller in ipv6_rpl_srh_rcv() then places the compressed header\nat buf + ((ohdr->hdrlen + 1) << 3). With hdrlen=0 this is buf + 8,\nbut the decompressed region occupies buf[0..2055] (8-byte header\nplus 128 full addresses). The compressed header overlaps the\ndecompressed data, and ipv6_rpl_srh_compress() writes into this\noverlap, corrupting the routing header of the forwarded packet.\n\nThe existing guard at exthdrs.c:546 checks (n + 1) > 255, which\nprevents n+1 from overflowing unsigned char (the segments_left\nfield), but does not prevent the computed hdrlen from overflowing\n__u8. n=127 passes because 128 <= 255, yet hdrlen=256 does not\nfit.\n\nTighten the bound to (n + 1) > 127. This caps n at 126, giving\nhdrlen = (127 * 16) >> 3 = 254, which fits in __u8. The compressed\nheader then lands at buf + ((254 + 1) << 3) = buf + 2040, exactly\npast the decompressed region (buf[0..2039]). No overlap. 127\nsegments is well beyond any realistic RPL deployment." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL" }, "scenarios": [ { "lang": "en", "value": "AV:N - The vulnerable code runs in the IPv6 routing-header receive handler on incoming packets; a remote attacker can deliver a crafted RFC 6554 type-3 RPL SRH to an RPL-enabled router or gateway over the network.\nAC:L - Triggering requires only a deterministically crafted SRH (e.g., n=127, CmprI=15, CmprE=15, pad=0, hdrlen=16, segments_left>0); all of these fields are fully attacker-controlled once the target has rpl_seg_enabled.\nPR:N - No authentication or local privileges are needed to send the malicious IPv6 packet; rpl_seg_enabled is a victim-side deployment setting on RPL routers/gateways (IoT/industrial mesh), not an attacker privilege requirement.\nUI:N - Exploitation is achieved solely by sending a malformed network packet and does not require any action from a victim user.\nS:U - Impact is confined to kernel memory corruption and packet forwarding within the same kernel security boundary; this is not a VM escape, sandbox escape, or cross-authority boundary violation.\nC:H - The hdrlen truncation causes overlapping read/write of the same kmalloc buffer during decompress/recompress, constituting kernel heap memory corruption that can be leveraged for information disclosure primitives.\nI:H - ipv6_rpl_srh_compress() performs out-of-bounds writes into the overlapping decompressed region, corrupting routing-header data that is then memcpy'd into the forwarded skb, enabling memory corruption exploitable for control-flow or data modification.\nA:H - Kernel heap corruption during SRH processing can cause kernel oops, panics, or repeated crashes when processing or forwarding the corrupted packet, consistent with high availability impact for memory-corruption bugs." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/ipv6/exthdrs.c" ], "versions": [ { "version": "8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3", "lessThan": "75b3680047bf09af8e7e471a7a6ddf2ce5847f56", "status": "affected", "versionType": "git" }, { "version": "8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3", "lessThan": "fd238c51b0fa5390cceca9f1ac5a9ffda8063eed", "status": "affected", "versionType": "git" }, { "version": "8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3", "lessThan": "3618b34942b76471d044369bfd30d58c39068bf1", "status": "affected", "versionType": "git" }, { "version": "8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3", "lessThan": "97e06791368c01f0ad2a4b3269c2abe19485ca32", "status": "affected", "versionType": "git" }, { "version": "8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3", "lessThan": "de02fc049352af5a9595f015511222d0a85c326b", "status": "affected", "versionType": "git" }, { "version": "8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3", "lessThan": "6fe1cb312038516cb4d9fa089d700af7059f1a64", "status": "affected", "versionType": "git" }, { "version": "8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3", "lessThan": "c0487a9c1e116cf349e2d1f302d9019670460858", "status": "affected", "versionType": "git" }, { "version": "8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3", "lessThan": "9d5e7a46a9f6d8f503b41bfefef70659845f1679", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/ipv6/exthdrs.c" ], "versions": [ { "version": "5.7", "status": "affected" }, { "version": "0", "lessThan": "5.7", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.259", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.210", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.176", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.143", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.93", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.35", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.0.12", "lessThanOrEqual": "7.0.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.7", "versionEndExcluding": "5.10.259" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.7", "versionEndExcluding": "5.15.210" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.7", "versionEndExcluding": "6.1.176" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.7", "versionEndExcluding": "6.6.143" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.7", "versionEndExcluding": "6.12.93" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.7", "versionEndExcluding": "6.18.35" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.7", "versionEndExcluding": "7.0.12" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.7", "versionEndExcluding": "7.1" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/75b3680047bf09af8e7e471a7a6ddf2ce5847f56" }, { "url": "https://git.kernel.org/stable/c/fd238c51b0fa5390cceca9f1ac5a9ffda8063eed" }, { "url": "https://git.kernel.org/stable/c/3618b34942b76471d044369bfd30d58c39068bf1" }, { "url": "https://git.kernel.org/stable/c/97e06791368c01f0ad2a4b3269c2abe19485ca32" }, { "url": "https://git.kernel.org/stable/c/de02fc049352af5a9595f015511222d0a85c326b" }, { "url": "https://git.kernel.org/stable/c/6fe1cb312038516cb4d9fa089d700af7059f1a64" }, { "url": "https://git.kernel.org/stable/c/c0487a9c1e116cf349e2d1f302d9019670460858" }, { "url": "https://git.kernel.org/stable/c/9d5e7a46a9f6d8f503b41bfefef70659845f1679" } ], "title": "ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()", "x_generator": { "engine": "bippy-1.2.0" } } } }